The goal of the proposed research is to provide to the radiotherapy community the design of medically practical generator of negative pi-meson beams of sufficient intensity and quality for therapeutic application. The research program for developing the various components of the pion-generator will be conducted with emphasis upon the constraints inherent in providing medical equipment which is to be intensively useful: compactness, reasonable construction and operating cost, reliability, and simplicity of operation. The end point of these studies will be a medical pion generator design compatible with typical hospital facilities with firmly established operating parameters and cost. The proposed work is based on the successful demonstration of the low beta RFQ accelerator under the current grant. The accelerator test facility includes injector, rf, RFQ accelerating structure, control, and instrumentation subsystems. Development projects in two major areas would be pursued in support of the overall research objective. The PIGMI technology would be further developed with the addition of a drift tube linac coupled to the RFQ accelerator bringing the final energy up to 5 MeV, and with fabrication and testing of a powered prototype of the high energy disk-and-washer accelerating structure. These development programs would culminate in a systems engineering study leading to the preliminary design of a hospital based accelerator utilizing the PIGMI technology which would provide therapeutic beams of pions.